Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add LichAmnesia/lich-skills --skill subagent-briefgit clone --depth 1 https://github.com/LichAmnesia/lich-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/lichamnesia/lich-skills/subagent-brief)<a href="https://agentmods.dev/skills/lichamnesia/lich-skills/subagent-brief"><img src="https://agentmods.dev/badge/skills/lichamnesia/lich-skills/subagent-brief.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.01534 |
| Opus 5 | $0.00000 | $0.00767 |
| Sonnet 5 | $0.00000 | $0.00307 |
| Haiku 4.5 | $0.00000 | $0.00153 |
Grade A, and why
subagent-brief scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 144 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Subagent Brief Discipline
Pre-flight checklist for spawning subagents in Claude Code. The single most expensive mistake in multi-agent workflows is treating subagents as free threads. They are not. Each subagent is an independent LLM call that re-tokenizes the entire prompt you hand it.
There is no prefix sharing across subagents in Anthropic's serving stack today. The multi-agent topology is a known optimization opportunity (see arXiv 2604.25899 Pythia: Predictability-Driven Agent-Native LLM Serving, 2026-04) but has not yet shipped in production. Until it does, the burden of compression falls on the orchestrating agent.
The math: 20 subagents × 50K shared context = ~1M tokens per fan-out. One careless Task call exhausts a Max-plan daily quota.
When to Use
- About to invoke the Task tool or any subagent-spawning tool
- About to fan out N parallel subagents on similar tasks
- Subagent prompt is shaping up longer than ~200 words
- About to embed a long file, full repo dump, or full PRD in a subagent prompt
- The user is on a metered plan (Max / Pro / API) and has not signaled "burn budget"
When NOT to Use
- Spawning a single subagent with a one-line task ("read X and summarize")
- The subagent genuinely needs the full document (translation, full audit, line-by-line review)
- Throwaway exploration where token cost truly does not matter
- The orchestrator already received a compressed brief from the user — pass it through, do not re-compress
The Discipline
For every subagent you are about to spawn, apply these five rules in order.
1. Strip your own context
The subagent gets its own system prompt, its own tool list, and its own task framing automatically. Do not paste your own conversation history, your TODO list, or your reasoning trail into the subagent prompt unless the subagent literally needs them to do its job.
2. Replace files with paths
BAD: Here is the full content of foo.py: <800 lines>
GOOD: Read /abs/path/to/foo.py and report the public API.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 144 lines · 0 tokens per session scan A fd117391525a
subagent-brief is a skill published in the GitHub repository LichAmnesia/lich-skills (233 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,534 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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